1. Field of the Invention
The present invention relates to an image forming apparatus of electrophotographic type such as an electrophotographic copying machine, an electrophotographic printer (for example, laser beam printer, LED printer or the like), a facsimile or a word processor, and a cartridge detachably attachable (mountable) to a main body of such an image forming apparatus.
2. Related Background Art
In conventional image forming apparatuses of the electrophotographic type, for example, a process cartridge in which developing means, an electrophotographic photosensitive member and process means acting on the photosensitive member are integrally incorporated as a cartridge unit, which can detachably be mounted to a main body of the image forming apparatus, has been used. According to such a process cartridge, since the maintenance of the apparatus can be effected by an operator himself without any serviceman (expert), the operability is enhanced considerably. Thus, the process cartridge has widely been used in the image forming apparatus.
However, the process cartridge has a limitation in a toner capacity and also has the following disadvantages.
That is to say, in case of an image forming apparatus permitting heavy duty operation, if a process cartridge having less toner capacity is used, since the frequency of exchange of process cartridges is increased, usability will be worsened. Further, when the process cartridge is exchanged for a new one, since constructural elements in the cartridge other than toner are also exchanged together, the running cost will be increased.
Thus, a so-called toner supplying system in which only toner is supplied and developing means and the like are provided in the main body has mainly been used in the heavy-duty copying machine. The disadvantage of the toner supplying system is that the maintenance of the apparatus, such as exchange of consumption (worn) part(s), can almost not be performed by the operator himself, requiring the expert for maintenance.
Recently, a process cartridge of the toner supplying type having advantages of both the process cartridge system and the toner supplying system has been proposed. An image forming apparatus using such a process cartridge of toner the supplying type includes a process cartridge comprising developing means for visualizing an electrostatic latent image formed on an image bearing member with toner, and a toner supplying unit for supplying a predetermined amount of toner to the developing means.
By the way, the developing means include two-component developer including toner and a carrier and toner density detecting means for detecting toner density (mixing ratio between the toner and the carrier) so that the toner density is maintained to a constant value by supplying the toner from the toner supplying unit in accordance with a detection value of the toner density detecting means.
Further, the developing means includes a start agent containing portion containing start agent in which the toner and the carrier are mixed together at a predetermined ratio and isolated from a developing portion by a seal member in order to prevent the start agent from leaking during transportation, and, when the process cartridge is newly used by the operator, the start agent can be supplied from the start agent containing portion by shifting the seal member.
It is desirable that the dispersion in detection outputs of respective process cartridges each having the toner density detecting means is corrected by measuring the toner density of the start agent in which the toner and the carrier are previously mixed together at a predetermined ratio by means of the toner density detecting means in the initiation of usage of the process cartridge. By using the correction sequence as an initial setting sequence of the process cartridge, the dispersion in detection output of the toner density detecting means with respect to the predetermined toner density can be corrected.
However, there is a case where the process cartridge is once dismounted from the main body of the image forming apparatus on the way and then is mounted to the main body again. In this case, if the correction sequence is effected again in the re-mounting, the waiting time will be increased to increase time loss. Further, since the toner density of the process cartridge on the way has slight dispersion in comparison with the toner density of the start agent, if the correction of the detection output of the toner density detecting means of the process cartridge being used is effected, the dispersion in detection output of the toner density detecting means for respective process cartridges may not be reflected correctly.
An object of the present invention is to provide a cartridge and an image forming apparatus, in which the above-mentioned correction sequence is effected only once for each cartridge.
Another object of the present invention is to provide a cartridge and an image forming apparatus, in which the waiting time can be reduced by avoiding repeated execution of a correction sequence.
A further object of the present invention is to provide a cartridge and an image forming apparatus, in which dispersion in detection output of toner detecting portions of respective cartridges can be corrected with high accuracy.
The other object of the present invention is to provide a cartridge and an image forming apparatus, in which information regarding execution of the correction sequence is stored in the cartridge.